Review of Combined Space and Domestic Hot Water Heating Systems for Solar Applications

Abstract

Solar heating systems are widely used in several European countries for domestic hot water heating, and in the past decade, an increasing number of solar combined space and hot water heating systems (typically referred to as “combisystems”) have begun to take precedence. In Canada, however, the majority of all residential solar thermal installations are for heating domestic hot water. To date, various combisystem configurations have been investigated under the auspices of the International Energy Agency, Task 26 and Task 32. Within these tasks, various system configurations were modelled and test procedures developed to allow standard performance evaluations to be conducted. This work, although extensive, has limited application within the North American context. At present, little research has been conducted on the applicability of these systems for residential housing. In particular, due to Canada’s more severe winters, larger solar collector arrays would be required to significantly contribute to the space heating load. This has drawbacks, as much of the solar capacity would not be utilized during the summer, leading to poor economic performance and possible overheating that could accelerate degradation or scald occupants. Therefore, there is a need to optimize the configuration of solar combisystems to avoid over-sizing while maximizing the utilization of solar energy in a safe and economic manner. This paper presents a review of the current literature on solar combined space and domestic hot water heating systems, with a particular emphasis on the work which has been conducted by the International Energy Agency. In addition, a review of combined space and domestic hot water systems currently installed in Canada are also discussed.